Network nodes forward packets using forwarding tables. Network nodes may take form in one or more routers, one or more bridges, one or more switches, one or more servers, or any other suitable communications processing device. A packet is a formatted unit of data that typically contains control information and payload data. Control information may include: source and destination IP addresses, error detection codes like checksums, sequencing information, etc. Control information is typically found in packet headers and trailers, with payload data in between.
Packet forwarding requires a decision process that, while simple in concept, can be complex. Since packet forwarding decisions are handled by network nodes, the total time required for this can become a major limiting factor in overall network performance.
Multiprotocol Label Switching (MPLS) is one packet forwarding mechanism. MPLS Nodes make packet forwarding decisions based on Label Distribution Protocol (LDP) distributed labels attached to packets and LDP forwarding tables. LDP is a process in which network nodes capable of MPLS exchange LDP labels (hereinafter labels). Packet forwarding based on labels stands in stark contrast to traditional Internet Protocol (IP) routing in which packet forwarding decisions are made by nodes using IP addresses contained within the packet.